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Avalanche Forecast

Archived

Dec 31st, 2023–Jan 1st, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Sky Pilot.

Carefully assess the bond of the recent snow with the old surface. Use caution anywhere the snowpack is thin and/or variable, where triggering is possible.

Confidence

Moderate

Avalanche Summary

Old evidence of isolated storm slabs from lee terrain, and small loose avalanches from steep southerly alpine features (size 1) may still be visible near Whistler. On Friday, very large persistent slabs (up to size 3) were naturally triggered on Decker Mountain and Panorama Ridge in Whistler, with wide propagation from shallow rocky alpine northern slope. These avalanches involved up to 100-120 cm deep persistent weak layers that resulted in wide propagations.

Snowpack Summary

10-20 cm of new snow may be found over a recent thin melt-freeze crust up to 2000 m. Underneath, 65 and 130 cm of soft snow and heavily wind-affected snow overlies a layer of poorly bonded crusts and surface hoar. These have shown sensitivity to natural and remote triggers over the last 3 days. The lower snowpack is strong and bonded.

The snowpack at treeline has been rain-saturated, and a surface crust may form soon with upcoming cooling. Total snow depths remain below average, with 60 to 80 cm at treeline.

Weather Summary

Sunday Night

Partly cloudy, no precipitation, alpine wind southwest 20 km/h, treeline temperature around -5 °C, freezing level at 1200 m.

Monday

Mostly sunny, no precipitation, alpine wind southwest 20 to 30 km/h, treeline temperature around -3 °C, freezing level at 1200 m.

Tuesday

Cloudy, 5-7 cm of snow, alpine wind southeast 40 to 50 km/h, treeline temperature around -1 °C, freezing level at 1400 m.

Wednesday

Cloudy with isolated flurries, trace accumulation, alpine wind southeast 20 km/h, treeline temperature around +0° C, freezing level at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Closely monitor how the new snow is bonding to the old surface.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.